>>529144290
>Sibling incest should be

There's your problem right there. Life doesn't operate under "should be" rules. Some sibling incest is cute, romantic and wholesome. Others are deeply abusive and horrifying. Just browse the recurring incest threads on /b/ to see the spectrum.

>lowly sexual desire

Spoilers: if you're starting from a baseline of "sex equals lowly and inferior" you're never going to have a healthy romantic relationship with anyone, sibling or otherwise.